Jose Mourinho turned away, fists pumping the air, arms raised in a defiant, provocative celebration. He roared and stormed down the tunnel, where a scuffle between both sets of players would soon erupt.

Jose Mourinho turned away, fists pumping the air, arms raised in a defiant, provocative celebration. He roared and stormed down the tunnel, where a scuffle between both sets of players would soon erupt.

This may have been a routine win for Manchester United, but it was a personal triumph for their manager.

Marouane Fellaini of Manchester United (L) and Rudy Gestede of Middlesbrough (R) battle to win a header. Photo by Matthew Lewis/Getty Images

Mourinho had just beaten the club who had dismissed one of his best friends, Aitor Karanka, a few days earlier.

His emotions bubbled on the surface throughout and even at the end, during the clashes in the tunnel with the home team, the fire inside still raged as he warned his hosts they would never be able to erase Karanka's name or his achievements on Teesside.

"People cannot delete the good things we do in clubs," Mourinho said. "Justice for Karanka is the work he did here.

"I was sacked by Chelsea. People, now, they don't like me, but nobody there can delete what we did.

Marcus Rashford of Manchester United (L) is put under pressure from Bernardo Espinosa of Middlesbrough. Photo by Stu Forster/Getty Images

"Aitor, he took them to the play-off final and could have left the club but decided to stay. He could have left the club - and I know what I'm saying. He could have left for better. He stayed for the fans, for the owner and for the players. He had a good opportunity to go to a bigger club. I repeat, I know what I'm saying. In the end, he loses his job."

Maybe it was the fact he felt his former assistant had been betrayed by Boro's players or, perhaps, it was merely because this was an important away win at the end of a gruelling run of games before the international break, but the Portuguese was in combative mood.

There was no handshake after the game on the touchline for Boro's new head coach, Steve Agnew, and there was little warmth from Mourinho towards the Middlesbrough players he felt conspired to get Karanka removed from the dugout.

Out of sight, on the fringes, but at the centre of it all, was Mourinho. His eyes will have twinkled.

Where there could have been lethargy, he had ensured there was enough fight for United to maintain their pursuit of a top-four finish.

After all, the Portuguese was worried his players would lose on Teesside, that they would be too exhausted to cope with a team fighting against relegation.

But there was no sign of fatigue, no hint of tiredness, no suggestion his players were suffering from a hectic schedule as they crushed Middlesbrough like a tank rolling over a bicycle.

According to Mourinho, United are vulnerable, weakened by the unfair demands placed on them. His players are being cruelly overworked, unnecessarily flogged by television companies for the enjoyment of armchair audiences.

Mourinho was able to make seven changes to the team who beat Rostov last Thursday night and still won easily.

That is why you have a squad and it is why United have one of the largest wage bills in Europe.

This win moved United up to fifth for the first time since September and they have not lost in the league since the end of October.

Mourinho's men are flying and this victory was a breeze once they had taken the lead though Marouane Fellaini after half an hour.

That lead was doubled by a wonderful strike from Jesse Lingard and, although Boro pulled a goal back through Gestede, the victory was confirmed when Antonio Valencia rolled the ball into an empty met after a stumble from former United goalkeeper Victor Valdes.

Valdes had been in inspired form up to that point, denying Marcus Rashford twice in the first half with wonderful saves. He also kept out a follow-up effort from Valencia.

It was a familiar story for United under Mourinho but did not follow the same script as the visitors eventually found a way past Valdes when Fellaini peeled off the back of left-back Fabio Da Silva to head in a deep cross from Ashley Young.

There were three Boro defenders inside the area to deal with Fellaini, but he managed to create an aerial duel with the smallest of them at the far post and won it comfortably.

In front and in control, United did not look as though there was any way a team that had not won a league game this year could trouble them.

Boro dominated possession and territory for 15 minutes at the start of the second half, but did nothing with it.

Unlike Lingard who, just affter the hour mark, picked up the ball on the halfway line after United had cleared a corner, galloped to the edge of the area as Boro's centre-backs retreated, and smashed an unstoppable shot into the top corner of the net. Even Mourinho allowed himself a smile.